U.S. patent application number 12/666258 was filed with the patent office on 2011-12-22 for user interfaces and associated apparatus and methods.
This patent application is currently assigned to NOKIA CORPORATION. Invention is credited to Marko Kalervo Karhiniemi, Turo Hermanni Keski-Jaskari.
Application Number | 20110310064 12/666258 |
Document ID | / |
Family ID | 38989873 |
Filed Date | 2011-12-22 |
United States Patent
Application |
20110310064 |
Kind Code |
A1 |
Keski-Jaskari; Turo Hermanni ;
et al. |
December 22, 2011 |
User Interfaces and Associated Apparatus and Methods
Abstract
Apparatus for a touch sensor, the apparatus comprising circuitry
for processing signaling to determine the detection of touch input,
wherein the circuitry for processing is arranged to detect touch
input by comparing touch signaling with one or more reference
thresholds, and wherein the circuitry for processing is arranged to
perform a first touch calibration, following the detection of the
first touch, to provide a first reference threshold which
compensates for the signaling associated with the first touch, and
wherein the circuitry for processing is arranged to detect a
subsequent next touch, using the first reference threshold, as the
reference threshold for detection of said next subsequent
touch.
Inventors: |
Keski-Jaskari; Turo Hermanni;
(Vantaa, FI) ; Karhiniemi; Marko Kalervo; (Espoo,
FI) |
Assignee: |
NOKIA CORPORATION
Espoo
FI
|
Family ID: |
38989873 |
Appl. No.: |
12/666258 |
Filed: |
June 25, 2007 |
PCT Filed: |
June 25, 2007 |
PCT NO: |
PCT/EP2007/005582 |
371 Date: |
August 20, 2010 |
Current U.S.
Class: |
345/178 |
Current CPC
Class: |
G06F 3/0418 20130101;
G06F 3/0445 20190501 |
Class at
Publication: |
345/178 |
International
Class: |
G06F 3/041 20060101
G06F003/041 |
Claims
1-24. (canceled)
25. An apparatus for a touch sensor, the apparatus comprising:
circuitry for processing signaling to determine the respective
locations of multiple concurrent touch inputs, wherein the
circuitry for processing is configured to: perform a first touch
calibration, following the detection of a first touch, to provide a
first reference threshold which compensates for the signaling
associated with the first touch, and detect the location of a
subsequent next concurrent touch, using the first reference
threshold, as the reference threshold for detection of the location
of said concurrent subsequent touch.
26. The apparatus according to claim 25, wherein the circuitry for
processing is configured to perform a second reference calibration,
following the detection of the first touch, to provide a second
reference threshold which compensates for the signaling associated
with the concurrent second touch, and wherein the circuitry for
processing is configured to detect a next concurrent third touch,
using the second reference threshold, as the reference threshold
for detection of said next concurrent third touch.
27. The apparatus according to claim 25, wherein the circuitry for
processing is for a touch sensor comprising a plurality of regions
defined for a user, and wherein the first touch is associated with
user touch of one of the regions defined for a user, and wherein
the concurrent second touch is associated with concurrent user
touch of another one of the regions defined for a user.
28. The apparatus according to claim 25, wherein the circuitry for
processing is for a touch sensor comprising a particular region
defined for a user, and wherein the first touch and one or more
subsequent concurrent touches are associated with multiple
selections using the same region for a user.
29. The apparatus according to claim 25, wherein the first touch is
configured to be associated with the provision of a menu of options
for user selection, and a subsequent concurrent touch is associated
with the selection of one of the menu options.
30. The apparatus according to claim 25, wherein the circuitry for
processing signaling is configured to: detect touch input; provide
additional signaling associated with the detected touch input; and
provide a reference threshold corresponding to said detected touch
by compensating for the additional signaling associated with said
touch.
31. The apparatus according to claim 30, wherein the circuitry for
processing is configured to remove the additional signaling
associated with said touch to provide the corresponding reference
threshold.
32. The apparatus according to claim 30, wherein: the circuitry for
processing is configured to detect touch input by detecting a
reduction in detected capacitance caused by a touch input; and the
additional signaling associated with the detected touch input is
configured to be representative of the detected reduction in
detected capacitance caused by said touch input.
33. The apparatus of claim 25, wherein the circuitry for processing
is configured to detect touch input by detecting a reduction in
detected capacitance caused by a touch input.
34. The apparatus of claim 25, wherein the circuitry for processing
is configured to: detect touch input by detecting a reduction in
detected capacitance caused by a touch input; provide additional
signaling associated with the detected touch input, the additional
signaling being configured to be representative of the detected
reduction in detected capacitance caused by said touch input; and
provide a reference threshold corresponding to said detected touch
by compensating for the additional signaling associated with said
touch.
35. The apparatus according to claim 25, wherein the circuitry for
processing is configured to perform an environment calibration to
provide an environment reference threshold to be used in the
detection of said first touch.
36. The apparatus according to claim 25, wherein the apparatus is
for a matrix type touch sensor or a capacitive shunt method touch
sensor.
37. The apparatus according to claim 25, wherein the circuitry for
providing signaling to determine the detection of touch input
comprises first and second mutually displaced dipole electrode
pairs, the pairs configured orthogonal to one another, to act as
sensors to detect changes in capacitance.
38. The apparatus according to claim 25, wherein the circuitry for
providing signaling to determine the detection of touch input
comprises a pulse circuit for measuring the capacitance to ground
of a plate.
39. The apparatus according to claim 25, comprising a touchpad to
provide a surface which can be used in the detection of touch
input.
40. An apparatus according to claim 25, wherein the apparatus is a
touch sensor, device, or module for a device.
41. A method for determining the locations of multiple concurrent
touches using a touch sensor apparatus, wherein the method
comprises: performing a first touch calibration, following the
detection of a first touch, to provide a first reference threshold
which compensates for the signaling associated with the first
touch, and detecting the location of a subsequent next concurrent
touch, using the first reference threshold as the reference
threshold for detection of the location of said subsequent
concurrent touch.
42. A computer program comprising computer code that is configured
to, when run, determine the locations of multiple concurrent
touches using a touch sensor, wherein the computer code is
configured to perform the steps of: performing a first touch
calibration, following the detection of a first touch, to provide a
first reference threshold which compensates for the signaling
associated with the first touch, and detecting the location of a
subsequent next concurrent touch, using the first reference
threshold as the reference threshold for detection of the location
of said concurrent subsequent touch.
43. A method of assembling an apparatus according to claim 25.
Description
TECHNICAL FIELD
[0001] The present invention relates to the field of user
interfaces, and in particular, touch user interfaces, including
so-called capacitive touch pads. Such (e.g. capacitive) touchpads
may be dedicated user input keypads which are not part of a
display, or may be comprised with a display such that they detect
user input over the display (i.e. a "touchscreen"). Associated
apparatus (including touch sensor modules for devices) and portable
electronic devices, and associated methods are also within the
scope of the present invention.
BACKGROUND
[0002] A touchpad is an input device commonly used in laptop
computers, but also increasingly used in portable electronic
devices such as Portable Digital Assistants (PDAs), including so
called mobile phones. They are used to detect user input, and
possibly also used to move a cursor, using motions of the user's
finger (or a suitable pen/stylus). In the case of a laptop, they
are a substitute for a computer mouse. Touchpads vary in size but
are currently rarely made larger than 20 square centimetres (about
3 square inches).
[0003] In general, touchpads operate by sensing the capacitance of
a finger (or other suitable input device e.g. appropriate stylus to
cause a change in detected capacitance), or the capacitance between
sensors. Capacitive sensors (comprising conductive elements) are
laid out along the horizontal and vertical axes of the touchpad.
The location of the finger is determined from the pattern of
capacitance from these sensors. In the case of using a pencil, as
the pencil tip is small and also because the pencil is not
conductive, the effect on the electric field is minimal and
therefore the capacitive sensors will not sense the tip of a pencil
or other similar implement.
[0004] Touchpads can be used to detect relative motion, such that
relative motion of the user's fingers can be used to cause relative
motion of the cursor. In such cases, the touch sensors most often
detect the absolute position of the finger, and appropriate
software is used to determine motion of the cursor. Depending on
the model of touchpad and drivers behind it, you may also click by
tapping your finger on the touchpad, and drag with a tap following
by a continuous pointing motion (a `click-and-a-half`).
[0005] Some touchpads also have so called "hotspots" (i.e. specific
predefined areas): locations on the touchpad that indicate user
intentions other than pointing. For example, on certain touchpads,
moving your finger along the right edge of the touch pad will
control the scrollbar and scroll the window that has the focus
vertically. Moving the finger on the bottom of the touchpad often
scrolls in horizontal direction.
[0006] There are two principal means by which capacitive touchpads
work; a so-called "matrix approach" and a "capacitive shunt
method".
[0007] In the `matrix approach` (i.e. a matrix type touch sensor),
a series of conductors are arranged in an array of parallel lines
in two layers, separated by an insulator. The conductors in these
layers are oriented orthogonally to one another. A high frequency
signal is applied sequentially between pairs in the two dimensional
matrix created by the conductor array. The current that passes
between the nodes is proportional to the capacitance. When a
virtual ground, such as the finger, is placed over one of the
intersections between the conductive layer some of the electrical
field lines are shunted to this ground point, resulting in a change
in the apparent capacitance at that location. This method received
U.S. Pat. No. 5,305,017
[0008] The `capacitive shunt method` senses the change in
capacitance between a transmitter and receiver that are on opposite
sides of the sensor. The transmitter creates an electric field
which oscillates at 2-300 kHz. If a ground point, such as the
finger, is placed between the transmitter and receiver, some of the
field lines are shunted away, decreasing the apparent
capacitance.
[0009] Capacitive touchpads which operate using an impedance
measurement principle (i.e. the "matrix approach") are easy and
cheap, but it normally just averages the point of contact to centre
of mass, and cannot distinguish two separate points of contacts
(i.e. multi-touch). In many applications, a multi-touch feature is
very useful, for example, pressing a shift key and then another
key. US20050046621A1 provides for recognizing two points from an
averaging touch screen, but it is based on the rapid change of the
position, after which the first position is evaluated to be the
first position, and the second is evaluated from the change of the
measured position. Thus, the teachings of this document may be
considered to be a "pseudo-method" to evaluate the other point, and
may not provide accurate results, for example, with very rapid
movements.
[0010] There are many ways in which one can utilise capacitive
signal detection to measure touch. It should also be appreciated
that the matrix method is sometimes defined by the sensor
arrangement and/or sensor arrangement and measurement principle.
However, in general, there are several measurement implementations,
which vary in measurement principle as well as sensor electrode
arrangement. These different measurement principles and sensor
arrangements form different electric fields around the electrodes,
with which the object (e.g. a finger or a stylus) interferes. The
measurement of this interference can be detected by a specific
measurement arrangement and corresponding method.
[0011] Due to the nature of electric field and the proximity of
multiple electrodes, the object usually affects the signal detected
by multiple electrodes, which can be problematic particularly in
detecting "multiple touch". This is particularly so in the case
that only a few electrodes are used, and the measurement principle
averages the whole detected capacitance over a touch surface. This
"averaging or shadow" effect can be compared to detecting the
central mass point of an object.
[0012] A good example of an averaging capacitance measurement
arrangement is a semi-conductive (e.g. 50 Ohm/square-500
kOhm/square) touch surface, where the capacitance signal over the
surface is measured e.g. from four corners. This is what is often
called impedance measurement because it uses the semi-conductive
surface which has a capacitive connection to the finger. The
measurement principle is described in U.S. Pat. No. 6,466,036 (a
pulse circuit for measuring the capacitance to ground of a plate),
and can also be applied to touch surfaces having semi-conductive
plane.
[0013] In short, this measurement principle uses the injection of
charge pulses from a number of electrodes (at least three,
advantageously at least four) placed around the touch plane.
Increased numbers of electrodes can be used for increased accuracy
and performance. These charge pulses generate electric field around
the semi-conductive plane, and the finger absorbs some of the
pulses (capacitive connection to the plane). The injected charges
are collected and counted to determine how many of those are needed
for reaching the threshold level. The sensing electrodes from the
corners of the touch plane have resistance values to the point
which forms the capacitance connection to the finger. Relative
resistance values determine the distances from the corners to
provide coordinate values. Linearity correction can be done via
software, but there exists some HW solutions as well: ITO striping
(US publication US 2006/0207806) and linearization patterning at
the edges of the foil.
[0014] A further example of a measurement principle which can be
used with a matrix type of grid sensor arrangement is described in
U.S. Pat. No. 6,452,514.
[0015] The listing or discussion of a prior-published document in
this specification should not necessarily be taken as an
acknowledgement that the document is part of the state of the art
or is common general knowledge. The present invention may use one
or more of the discussed measurement principles or other
measurement principles not discussed. The present invention may not
necessarily be limited to capacitive touch sensors, or touch
sensors known at the time of filing.
SUMMARY
[0016] In a first aspect, there is provided an apparatus for a
touch sensor, the apparatus comprising: [0017] circuitry for
processing signaling to determine the detection of touch input,
wherein the circuitry for processing is arranged to detect touch
input by comparing touch signaling with one or more reference
thresholds, and wherein the circuitry for processing is arranged to
perform a first touch calibration, following the detection of the
first touch, to provide a first reference threshold which
compensates for the signaling associated with the first touch, and
wherein the circuitry for processing is arranged to detect a
subsequent next touch, using the first reference threshold, as the
reference threshold for detection of said next subsequent
touch.
[0018] The circuitry for processing may be arranged to perform a
first touch calibration, following the detection of the first
touch, to provide a first reference threshold which compensates for
the signaling associated with the first touch, and the circuitry
for processing may be arranged to detect a next second touch, using
the first reference threshold, as the reference threshold for
detection of said next second touch.
[0019] The first touch may be the very first touch in a sequence of
touches, or an intermediate touch in a sequence of touches.
[0020] The circuitry for processing may be arranged to perform a
second reference calibration, following the detection of the first
touch, to provide a second reference threshold which compensates
for the signaling associated with the second touch, and the
circuitry for processing may be arranged to detect a next third
touch, using the second reference threshold, as the reference
threshold for detection of said next third touch.
[0021] This second reference threshold would also inherently
compensate for the signaling associated with the first touch as the
second touch was detected based on compensation for the signaling
associated with the first touch.
[0022] The circuitry for processing may be for a touch sensor
comprising a plurality of regions defined for a user, and the first
touch may be associated with user touch of one of the regions
defined for a user, and the second touch may be associated with
user touch of another one of the regions defined for a user.
[0023] The regions defined for a user may comprise respective key
regions, for example, of a (e.g. QWERTY) keyboard-type user
interface.
[0024] The circuitry for processing may be for a touch sensor
comprising a particular region defined for a user, and the first
touch and one or more subsequent touches may be associated with
multiple selections using the same region for a user.
[0025] The first touch may be arranged to be associated with the
provision of a menu of options for user selection, and a subsequent
touch may be associated with the selection of one of the menu
options.
[0026] The touch sensor may be arranged such that touch is
associated with a reduction in detected capacitance. The reduction
in detected capacitance may be associated the provision of
additional signaling compared to when touch is not detected. The
detection of touch may be associated with additional signaling
compared to when touch is not detected.
[0027] The circuitry for processing signaling may be arranged to
detect touch input, based upon additional signaling associated with
touch, and to provide the first reference threshold by compensating
for the additional signaling associated with the first touch.
[0028] The circuitry for processing may be arranged to remove the
additional signaling associated with the first touch to provide the
first reference threshold.
[0029] The circuitry for processing may be arranged to perform an
environment calibration to provide an environment reference
threshold to be used in the detection of said first touch. The
environmental calibration may compensate for the effect of one or
more of device covers, the sensor layout, the PCB underneath the
sensor, wirings, metal parts, user's hand(s), etc on the touch
detection mechanism/measurement principle.
[0030] The apparatus may be arranged to automatically perform the
environment calibration upon powering up of the apparatus. The
apparatus may be arranged to perform the environment calibration at
predefined intervals following powering up of the apparatus. The
apparatus may be arranged to perform the environment calibration
continuously following powering up of the apparatus until a first
touch is detected.
[0031] The apparatus may be arranged to store one or more reference
thresholds in associated memory circuitry.
[0032] The circuitry for processing may be arranged to wait for a
predetermined time period, following the detection of the first
touch, before performing the first touch calibration.
[0033] The apparatus may comprise circuitry for providing signaling
to determine the detection of touch input.
[0034] The apparatus may be for a matrix type touch sensor.
[0035] The circuitry for providing signaling to determine the
detection of touch input may comprise first and second mutually
displaced dipole electrode pairs, the pairs arranged orthogonal to
one another, to act as sensors to detect changes in
capacitance.
[0036] The circuitry for providing signaling to determine the
detection of touch input may comprise a pulse circuit for measuring
the capacitance to ground of a plate.
[0037] The apparatus may be for a capacitive shunt method touch
sensor.
[0038] The apparatus may comprise a touchpad to provide a surface
which can be used in the detection of touch input.
[0039] In a second aspect, there is provided a touch sensor
comprising the apparatus for a touch sensor.
[0040] In a third aspect, there is provided a device comprising the
apparatus for a touch sensor.
[0041] In a fourth aspect, there is provided a module for a device,
the module comprising the apparatus for a touch sensor.
[0042] In a fifth aspect, there is provided a method for the
detection of a plurality of touches using a touch sensor apparatus,
the method involving the detection of touch input by comparing
touch signaling with one or more reference thresholds, wherein the
method comprises performing a first touch calibration, following
the detection of a first touch, to provide a first reference
threshold which compensates for the signaling associated with the
first touch, and using the first reference threshold as the
reference threshold for detection of a next subsequent touch.
[0043] In a sixth aspect, there is provided a computer program
comprising computer code arranged to provide the detection of a
plurality of touches using a touch sensor, the computer code
arranged to detect touch input by comparing touch signaling with
one or more reference thresholds, wherein the computer code is
arranged to perform a first touch calibration, following the
detection of a first touch, to provide a first reference threshold
which compensates for the signaling associated with the first
touch, and use the first reference threshold as the reference
threshold for detection of a next subsequent touch.
[0044] Associated methods of assembly of apparatus/devices are also
provided.
[0045] In a seventh aspect, there is provided an apparatus for a
means for touch sensing, the apparatus comprising:
[0046] means for processing signaling to determine the detection of
touch input, wherein the means for processing is arranged to detect
touch input by comparing touch signaling with one or more reference
thresholds, and wherein the means for processing is arranged to
perform a first touch calibration, following the detection of the
first touch, to provide a first reference threshold which
compensates for the signaling associated with the first touch, and
wherein the means for processing is arranged to detect a subsequent
next touch, using the first reference threshold, as the reference
threshold for detection of said next subsequent touch.
[0047] The circuitry for processing may be processing circuitry and
the circuitry for providing signaling to determine the detection of
touch input may be touch input detection circuitry.
[0048] It will be appreciated that one or more aspects/embodiments
provide that after a recognised "touch event", the whole measured
(e.g. capacitive) field around the sensor will be compensated so
that the touching finger becomes part of the environment i.e. part
of the background. This would involve the updating of the threshold
to provide a new compensated threshold. Whereas the original
environment calibration (prior to the first touch) would take
account of the impact of, for example, any device covers, the
holding hand, etc, following the "first touch event", the impact of
the first touch on the measured (e.g. capacitive) field would also
be considered to be part of the background following the first
touch, and be used to assess whether there has been a subsequent
second touch.
[0049] The present invention includes one or more aspects,
embodiments or features in isolation or in various combinations
whether or not specifically stated (including claimed) in that
combination or in isolation. Corresponding means for performing one
or more of the functions discussed are also within the present
disclosure.
[0050] The above summary is intended to be merely exemplary and
non-limiting.
BRIEF DESCRIPTION OF THE FIGURES
[0051] A description is now given, by way of example only, with
reference to the accompanying drawings, in which:--
[0052] FIG. 1 illustrates a model showing how a matrix type touch
sensors according to the prior art detects multiple touches;
[0053] FIG. 2 illustrates a model showing how a matrix type touch
sensor according one embodiment of the present invention detects
multiple touches;
[0054] FIG. 3 compares the capacitive signaling level in the prior
art of FIG. 1 (FIG. 3a) with that of the embodiment of FIG. 2 (FIG.
3b);
[0055] FIG. 4 shows an application of a touch sensor according to
one embodiment of the present invention;
[0056] FIG. 5 shows a schematic representation of a touch sensor
according to one embodiment of the invention;
[0057] FIG. 6 shows some details of the circuitry for detecting
touch of FIG. 5;
[0058] FIG. 7 shows the schematic representation of a capacitive
shunt touch sensor which can be used in another embodiment of the
present invention; and
[0059] FIG. 8 provides a flowchart of a method of calibration
according to one embodiment.
DESCRIPTION OF SPECIFIC EMBODIMENTS
[0060] Before describing the operation of the present invention, it
would be useful to understand how a matrix-type capacitive touch
sensor according to the prior art detects multiple touches. This is
modeled in FIG. 1.
[0061] Firstly, the touch sensor performs an environmental
(background) calibration some time prior to the detection of a
first touch. This environmental calibration provides a reference
threshold level ((B1, FIG. 3a)) of capacitance which is used to
determine whether touch has been detected or not. If touch has been
detected, then the detected capacitance changes (i.e. reduces) and
the capacitance signal level detected changes (i.e. increases),
signal level FT as shown in FIG. 3a. As shown in FIG. 3a, the
capacitance signal level correspondingly increases with each
additional touch (signal level ST), and correspondingly reduces
which removal of each touch (signal level RS associated with the
removal of the second touch (leaving the first touch only), and
signal level RF/B2 with the subsequent removal of the first touch
to a second background level). Once all touches have been removed,
the capacitive signal level reverts to (or very near to) that
associated with the environmental (background) calibration (B1,
B2). An environmental re-calibration may be required.
[0062] In the prior art, a first touch is correctly detected (see
FIG. 1). However, when a user at the same time touches the touchpad
in a different region ("real finger touch point" of FIG. 1), the
touch sensor "averages" the capacitance measurement and incorrectly
assumes that the user has touched the touchpad in a region
equidistant between the actual first and second touches (i.e. the
averaged second touch). In other words, the detected second touch
shown in FIG. 1 does not correspond to the actual second touch, but
an average of the two touch positions. In the prior art, both
touches are determined based on changes in detected capacitance
level compared to the originally determined environmental reference
threshold. The environmental threshold is not reset between
touches.
[0063] In accordance with one embodiment of the present invention
(FIG. 2, and FIG. 3b), the touch sensor does not average the two
touch positions. As in the case of the touch sensor of FIG. 1, the
first touch (FT) is determined based on a comparison of the
detected capacitance level with the environmental reference
threshold (i.e. comparison with a previous reference threshold
B1).
[0064] However, following detection of the first touch FT (and
registering of the position of the first touch), a further
calibration is performed. This second calibration takes into
account the impact of the first touch on the detected capacitance
signal level (and can be considered to reset the background
capacitive signal level, or provide a new background level B2).
This second calibration provides a new reference threshold B2 which
is then used to determine whether a further touch (ST) is made. In
this way, the two touches FT, ST can be individually detected (FIG.
3b). After detection of the second touch ST, a further calibration
is performed to take into account the present of the second touch.
This provides a further new background reference level B3. The new
background reference level B3 is used to detect the removal of the
second touch (RS). In this case, the capacitive signal level RS,
following removal of the second touch, is detected to be negative
compared to the reference threshold B3. A further reference
calibration is performed following removal of the second touch to
provide a new reference signal level B4 which is used to detect the
subsequent removal of the first touch. Similarly, the removal of
the first touch is detected as a negative signal level RF compared
to the previous signal level B4. A further calibration is performed
following the removal of the first touch to provide a new reference
signal level B5.
[0065] In summary, following the calibration after the detection of
the first touch input, the sensor "sees" the first touch point as a
normal feature of the surrounding environment and ignores it. After
that, any new signal change can lead to the position of the second
finger. In this way, at least 2 different locations can be found
with reasonable accuracy, which enables, for example, modifier
(e.g. Shift/Ctrl) key+letter key combination usage, or an area
selection from an image, for example. As explained, this principle
can be applied to further subsequent touches by re-calibrating
between respective touches. The touch sensor can be used in various
devices, including PDAs, and audio/video players/recorders and
other (in particular portable) electronic devices which require
user interfaces.
[0066] It will be appreciated that additional operations can be
applied with (e.g. at the same time, or following) one or more of
the calibrations. For example, a coordinate map could be applied to
the touch area to linearize, enhance performance or enable
additional functionality. This can be based on the calibrated
threshold value (the additional operations being performed if the
threshold value changes by at least a predetermined amount). For
example, if the calibration to the environment (i.e. the "vanishing
the effect of finger") is done, and the new threshold level is
considered to be a significant change, then the additional
operation are performed. Furthermore, a series of calibration can
be performed (rather than a single calibration step), for example
in the frequency of 10 Hz, to provide a averaged new threshold
level.
[0067] FIG. 4 shows a practical example of the use of a touch
sensor according to one embodiment. The touch sensor can be
advantageously used in providing QWERTY keyboard user input by
defining specific regions on the touchpad surface associated with a
particular entry value.
[0068] It is also possible for the present invention to be used in
the touchpad of, for example, laptops allowing the performance of
"right-click mouse options". For example, a first touch could
provide a menu of options on a display, which could be selected by
a second subsequent touch on a different region of touchpad (these
different regions not in-themselves being predefined to a user as
different regions of the touch pad allowing for entry of a
particular value associated with that particular region).
[0069] It will be appreciated that embodiments of the invention can
be applied to existing types of touch sensors with modifications to
software only (and with minimal, if any, modifications to
hardware). The invention can also be applied to new types of touch
sensors.
[0070] FIG. 5 shows a schematic illustration of a matrix type
capacitive touchpad sensor 100 in accordance with one embodiment of
the present invention. It comprises a capacitive touchpad sensor
arrangement 20 (circuitry for detecting touch) and balance
measurement and recalibration logic 10 (circuitry for processing
the detection of touch).
[0071] The capacitive touchpad sensor arrangement 20 comprises a
touchpad surface (not shown) under which are laid a series of
electrodes 21, 22, 23, 24 provided in respective layers in a
mutually orthogonal matrix configuration. A dielectric material D
is provided between the respective layers (FIG. 6). For simplicity,
only one pair of electrodes are shown in each layer in FIG. 6. It
will be appreciated that the pairs of electrodes overlie one
another to define (in this case four) regions A which can act as
capacitors.
[0072] As shown in FIG. 6, the conductive elements 21, 22, 23, 24
are configured in parallel pairs that form the columns and rows of
a matrix configuration. The electrodes are arranged in adjacent
dipole pairs such that capacitance signaling provided by the
respective pairs are out of phase with one another. These
electrodes are connected to the balance measurement and
recalibration logic 10 through connections which provide
capacitance signaling values R+, R-, C+ and C-.
[0073] The outputs of the touchpad sensor arrangement 20 are in an
equilibrious state when under steady state conditions such as after
boot up or when the device is held in a user's hand (i.e. following
a calibration). Touch points between a grounded conductive element,
such as a user's finger, and the touchpad sensor arrangement 20 are
registered in both event and position by the balance output B. The
output B can be considered to be the capacitive signal level of
FIG. 3.
[0074] The balance measurement and recalibration logic 10 can be
used to recalibrate the touchpad sensor arrangement 20 outputs R+,
R-, C+ and C- after respective touch events (removal or addition of
a touch) so as to return them to the equilibrium as experienced
under steady state conditions (reset to the background level). Any
subsequent touch point on the touchpad sensor arrangement 20 is
"seen" by the balance measuring and recalibration logic 10 as a
single touch point, and the position of the second touch can be
calculated.
[0075] FIG. 7 shows a schematic representation of a capacitive
shunt type method. Using this method, an excitation source is
connected to a transmitter generating an electric field to a
receiver. The field lines measured at the receiver are translated
into the digital domain by a .SIGMA.-.DELTA. converter. When a
finger, or other grounded object, interferes with the electric
field, some of the field lines are shunted to ground and do not
reach the receiver. Therefore, the total capacitance measured at
the receiver decreases when an object comes close to the induced
field. As with the previous embodiment, a calibration can be
performed following (e.g. each) touch event so as to account for
the previous touch event when detecting the next touch event.
[0076] It should be noted that detection of a touch does not
necessarily require a user to touch the touch pad surface. For
example, a change in capacitance will be detected if the user
finger approached near to the surface of the touchpad surface.
[0077] It will be appreciated that one or more aspects/embodiments
provide that after a recognised "touch event", the whole measured
(e.g. capacitive) field around the sensor will be compensated so
that the touching finger becomes part of the environment i.e. part
of the background. This would involve the updating of the threshold
to provide a new compensated threshold. Whereas the original
environment calibration (prior to the first touch) would take
account of the impact of, for example, any device covers, the
holding hand, etc, following the "first touch event", the impact of
the first touch on the measured (e.g. capacitive) field would also
be considered to be part of the background following the first
touch, and be used to assess whether there has been a subsequent
second touch (FIG. 8).
[0078] It will be appreciated that the aforementioned circuitry may
have other functions in addition to the mentioned functions, and
that these functions may be performed by the same circuit.
[0079] The applicant hereby discloses in isolation each individual
feature described herein and any combination of two or more such
features, to the extent that such features or combinations are
capable of being carried out based on the present specification as
a whole in the light of the common general knowledge of a person
skilled in the art, irrespective of whether such features or
combinations of features solve any problems disclosed herein, and
without limitation to the scope of the claims. The applicant
indicates that aspects of the present invention may consist of any
such individual feature or combination of features. In view of the
foregoing description it will be evident to a person skilled in the
art that various modifications may be made within the scope of the
invention.
[0080] While there have been shown and described and pointed out
fundamental novel features of the invention as applied to preferred
embodiments thereof, it will be understood that various omissions
and substitutions and changes in the form and details of the
devices and methods described may be made by those skilled in the
art without departing from the spirit of the invention. For
example, it is expressly intended that all combinations of those
elements and/or method steps which perform substantially the same
function in substantially the same way to achieve the same results
are within the scope of the invention. Moreover, it should be
recognized that structures and/or elements and/or method steps
shown and/or described in connection with any disclosed form or
embodiment of the invention may be incorporated in any other
disclosed or described or suggested form or embodiment as a general
matter of design choice. It is the intention, therefore, to be
limited only as indicated by the scope of the claims appended
hereto. Furthermore, in the claims means-plus-function clauses are
intended to cover the structures described herein as performing the
recited function and not only structural equivalents, but also
equivalent structures. Thus although a nail and a screw may not be
structural equivalents in that a nail employs a cylindrical surface
to secure wooden parts together, whereas a screw employs a helical
surface, in the environment of fastening wooden parts, a nail and a
screw may be equivalent structures.
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